How Accurate a Straight Edge Needed?

[Gary Curtis]

To set up and align new cabinet saw with sliding table. Veritas sells a steel straight edge, 2 feet, true to .001". An aluminum one at 3 feet, true to .003".

Kind of pricey . How accurate must it be to do the job?

Gary Curtis

[Bob Smalser]

I've used a common aluminum yardstick or its ilk for such tasks quite successfully for 4+ decades.

It's rarely the tools....

[martyphee]

I have both of those and to be honest that is cheap as hell for that accuracy IMHO. I used the 3 footer for aligning my jointer beds (16" jointer 7' long). Look at the price of a starret of the like. The price goes up exponentially with length.

How accurate do you want it. If your just talking flatness between the two a simple straight edge and a light will tell you when their flat.

[Don Baer]

After watching Sam Maloof use his thum on a pencil to do some demensioning I'm about ready to throw away all of my mesauring sticks.

[Todd Franks]

<st1:city><st1 ="">Gary</st1></st1:city>,

<!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:stroke joinstyle="miter"/> <v:formulas> <v:f eqn="if lineDrawn pixelLineWidth 0"/> <v:f eqn="sum @0 1 0"/> <v:f eqn="sum 0 0 @1"/> <v:f eqn="prod @2 1 2"/> <v:f eqn="prod @3 21600 pixelWidth"/> <v:f eqn="prod @3 21600 pixelHeight"/> <v:f eqn="sum @0 0 1"/> <v:f eqn="prod @6 1 2"/> <v:f eqn="prod @7 21600 pixelWidth"/> <v:f eqn="sum @8 21600 0"/> <v:f eqn="prod @7 21600 pixelHeight"/> <v:f eqn="sum @10 21600 0"/> </v:formulas> <v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/> <o:lock v:ext="edit" aspectratio="t"/> </v:shapetype><v:shape id="_x0000_i1025" type="#_x0000_t75" alt="" style='width:12pt; height:12pt'> <v:imagedata src="file:///C:\DOCUME~1\Todd\LOCALS~1\Temp\msohtml1\01\clip_im age001.gif" o:href="http://sawmillcreek.org/images/smilies/biggrin.gif"/> </v:shape><![endif]--><!--[if !vml]--><!--[endif]--> I used a 4' Empire aluminum yardstick to align my cabinet saw, jointer, and planer. Being an engineer that is anal about stuff (redundant:D) I eventually bought the Veritas 24" steel straightedge. After rechecking my machines with the new straightedge I couldn't find anything that needed fixin'. The largest error between my alum yardstick and Veritas straightedge is .003" along their entire length. For me it's piece of mind to have an accurate straightedge, but to reiterate Bob and Don's point, the quality of my furniture is no better because of it. You sometimes need 3 hands with the alum yardstick because it cannot stand on its side due to its narrow thickness. In this regard the accurate straightedges are better and because of this the 50" Veritas alum straightedge is on my wish list. From my experience the accurate straightedges are nice, but a good quality level or cheap straightedge will work just fine too.

-Todd

[Mark Singer]

I have a couple of inexpensive "T" squares...A 3' straight edge that is made by Pacific Arc and is decent... I have several long levels which are just ok as traight edges...as Bob said it is not that critical. They are all straighter than we can cut with a hand or power saw of any variety...

[Dev Emch]

Depends on what your doing. Thats the bottom line. If your using it for woodworking, then look at your reference edge. Got a good reference edge from the jointer? Then use your hand to hold a pencil along with a simple square and run the line. If you can hold your fingers still, then maloof it.

I have an old B&S camel back straight edge which is a gosh darn accurate edge. It was used for building machine tools. I only use it to align and dial in machines. I have never used this for woodworking.

In woodworking, often the scriber and eyeball are more accurate than some fancy straight edges. You can still make a bone head mistake with a starrett.

[Bob Smalser]

I might even use one of my leaf feeler gages with that yardstick. But mostly I use matchbook covers or business cards to measure that kind of clearance. ;)

[Paul Canaris]

Get a precision ruler or two..There are several sources for these, some are ground to .001" per foot on the edge. This approach has the added advantage of providing you with rulers which you will need anyway. Their thin and won't stand on edge easy, so I use welder 90 degree magnets to do this...works very well.

[Bob Johnson2]

I also use a metal yardstick or if I need it longer a 4' level held up on edge.

[Frank Pellow]

I have the Veritas 38 inch aluminum straight edge and I did use it when first setting up my machines. It is quite reassuring, but probably overkill for me. The Veritas straight edge did confirm that the side of my 4 foot level is very accurate and I now mostly use that leval to check things for staightness.

[Jay Goddard]

I purchased an inexpensive aluminum straight edge from Sears for less than $10. I took it to work and measured it on a granite surface plate and was not able to fit a .0015" feeler guage under any part of it. Definitely accurate enough for machine setup!

Like Todd I found it to be hard to set on edge. But I managed to make it work by attaching a small bar clamp to it while it was standing on edge.

Jay

[Gary Curtis]

After reading Jay's post, I'm headed for Sears. $10 definitely fits in with my 5-year plan. My reason for the post is the sliding table part of this saw. I've concerns on other forums about aligning sliding tables. The instructions outline procedures to get the surfaces aligned in 3 axis.

The thing has 60 inches of travel, so it seemed that misalignments might be magnified over that motion range. Another approach might just be to use the unmounted crosscut fence and feeler gauges. That out to have pretty close tolerances.

Thanks for all your suggestions. I'm too old to start thinking in angstrom units.

Gary Curtis

[lou sansone]

I've used a common aluminum yardstick or its ilk for such tasks quite successfully for 4+ decades.

It's rarely the tools....

amen .... thank you bob for your seasoned wisdom..

lou

[David LaRue]

Gary,

Perhaps you could use, or borrow a laser level for one of the axis' (horizontal) as a reference for the other two?

[tod evans]

gary, bob has given you good advice. if i need something dead on i use a bar of knife steel `cause that`s something i keep in stock but for 95% of tool set up i rip a straight piece of baltic and use it. .02 tod

[Gary Curtis]

The folks who manufactured my Sliding Table Saw gave me their answer on this matter. General of Drummondville, Canada

As far as the table tops on the saw and the slider are concerned, .015" co-planer is adequate. So a hardware store straight edge will do. Alignment of the ball bearing mounts at the edge of the cabinet saw, acceptable tolerance is .002" (two thousands). Adjustment on the Outrigger Guide bar should keep the slider level to within .020" (twenty thousands) through the entire sweep.

These limits will keep the crosscut fence at 90 degrees angle to the blade, unless set for a miter cut. So the closest slider edge to the blade requires 10 times the accuracy of the far left edge. For me, that means a digital dial gauge to check the right side, and a reasonable 4' straight edge and auto feeler gauges for the left side.

They did mention that some users, and some work, might call for better co-planar numbers on the top. Thanks to all for their input. I'm headed to Sears.

Gary Curtis